1. Field of the Invention
The disclosure relates generally to apparatus and methods for assembling and disassembling pipe joints for well drilling, production, maintenance, or combinations thereof. More particularly, the disclosure relates to a pipe joint rack unit configured to independently store at least two pipe joints below the drilling deck and to aid in the coupling of tubulars.
2. Background of the Technology
Oil and gas well systems employ numerous types of elongated tubulars including, for example, drill pipes, casings, and collars that are coupled together end-to-end. For ease of handling, groups of two or more individual tubulars are commonly joined together to form “stands.” These stands may then be coupled to form a longer series of coupled tubulars called a “string.” Various types of strings are known in the oil and gas industry based on the task performed, e.g., drill strings for drilling, completion string for completion operations, and production string for producing hydrocarbons. The operation of constructing stands and ultimately constructing a long “string” of joined tubulars and running the string into a borehole, or a well, is performed primarily on a drilling floor or drilling deck. The operation of retrieving a pipe string from the borehole, or well, and dismantling the pipe string into separate stands or pieces of pipes is likewise performed primarily on a drill floor.
Each individual pipe or tubular is threaded at both ends. To couple two or more pipes into a pipe stand, an end of one pipe is threaded, or screwed, into the end of the other pipe. Conversely, to decouple two pipes, one pipe is unthreaded from the other pipe until disengaged. In some instances, the coupling and decoupling operations are accomplished using motor-driven tools.
To increase the efficiency of the assembly or disassembly of stands and strings, some pipe coupling or decoupling procedures are performed in an area located outside of or remote to the central area of the drill floor, i.e. away from the center of the borehole, or well. For example, sets of individual pipes may be initially assembled into a pipe stand in the remote area outside the central area. The assembled pipe stand may then be moved into the central area for connection to a downhole string. Alternatively, a pipe string may be dismantled into two or more pipe stands in the central area. Each pipe stand is then moved into the remote area for further disassembly. In each scenario, the assembly or disassembly procedures are distributed between two or more areas of the drill floor.
Typically during assembly or disassembly of pipe stands, each piece of pipe is solitarily and temporarily disposed in a storage area provided by a substantially vertical tubular housing located in or below the drilling deck. The housing is open at its upper end and includes a pipe support at its lower end. The tubular housing is installed such that its open upper end is concentrically disposed about a mousehole in the drilling deck, which provides access to the housing. The pipe support may be an end or bottom plate. The depth of the storage area within the housing is determined by the positioning of the pipe support.
To assemble four pipes into a four-pipe stand, a first pipe is placed in the tubular housing, a second pipe is brought to a vertical position above the first pipe and then lowered to engage the first pipe. The two pipes are screwed together to form a first “two-pipe stand” by use of a tool located proximate the mousehole on the drilling deck. The first two-pipe stand is lifted from the vicinity of the mousehole and placed in an intermediate storage area. Next, a second “two-pipe stand” is constructed in the shallow tubular housing following the same steps. The second two-pipe stand is transferred through another mousehole in the drilling deck into a deeper tubular housing, so that the upper end of the second two-pipe stand can be positioned at a suitable working height above the drill floor. The first two-pipe stand is retrieved from the intermediate storage area and coupled to the top of the second two-pipe stand located in the deeper tubular housing to complete the four-pipe stand. The four-pipe stand is lifted and brought to the central area of the drill floor, or placed in the intermediate storage area. Disassembly of the four-pipe stand is accomplished using substantially the same steps but performed in the opposite order.
A drawback of the above-described assembly and disassembly operations is the need for tubular housings having different depths (to accommodate a single pipe vs. a two pipe stand) or need to adjust the depth of the storage area within the housing. Another potential drawback of these operations is the need to move pipe stands between housing of differing depths or between a tubular housing and an intermediate storage area. Such adjustments and movements increase the time required to complete the operation and thus reduce the assembly or disassembly operation efficiency. Furthermore, in designs wherein the tubular housing itself moves with respect to the surroundings, there is potential for the device to entangle nearby wires, flexible conduit, or other features under the drilling deck. Accordingly, there remains a need in the art for apparatus and methods that increase the efficiency of pipe assembly or disassembly operations.